The quality control and production processes typically employed by the semiconductor production industry often include as an integral part of the microfabrication process the formation of intended thin-film on semiconductor substrates. The semiconductor substrates typically are in the form of wafers to be coated, and are loaded in quartz boats that are removably inserted into a depositing furnace. Reactants in gas phase are injected into the furance and are catalyzed by the surface of the semiconductor wafers to deposit as a thin-film thereon. After thin-film formation the wafers are withdrawn from the furnace and the same or another reaction is performed on the same or another batch of semiconductor wafers.
The dimensions and other characteristics of the thin-film and of the intended device to be fabricated thereby are often such that any particulates or other pollution generated in the coating process can ruin the batch of wafers. A high degree of cleanliness is thus required in handling the wafers to circumvent and minimize the contamination problem.
The boats in which the semiconductor substrates are loaded are typically fabricated of quartz or other refractory material, and the substrates themselves are constituted as thin wafers of silicon or other fragile semiconductor materials. The quartzware boats and wafers loaded therein thus require precision handling to avoid any movement-induced damage such as unintended quartzware and/or substrate chipping, breaking, and the like.
The processing time throughput of the thin-film forming processes is determined by the boat to furnace transfer times during loading and unloading. Revenue generation in the use of the furnace depends upon the system throughput time. Thin-film deposition systems are thus called upon to minimize the "dead time" between batches of wafer-loaded boats to be coated and in such a way as to readily accommodate the requirements of anyone of several run-time deposition processes.
It is thus desirable to provide a boat transfer and queuing furnace elevator and method that is at once free of unacceptably high pollution generation, sufficiently controlled to resist undesirable breakage during transfer, and fast and flexible enough to maximize revenue generation in a manner that readily allows the implementation of any one of several run-time deposition reactions.